In this article we claim that stone classifier-based numeral systems in a number of unrelated North-western South American language families/languages such as Kawapanan, Cholón-Hibito, Munichi, and, tentatively, Quingnam emerged due to calquing or loan translation (Weinreich 1963; Epps 2006, 2013). In addition, although the donor language remains unknown, we argue for this to be a case of a poorly attested grammaticalisation path of numeral classifiers and numerals, namely STONE>CLASSIFIER, as presented in Conklin (1981), for languages such as Gorontalo, Kam-Muang, White Tai and Western Austronesian languages (Conklin 1981, 233, 234; mentioned by Aikhenvald 2000, 446). Moreover, ethnohistorical and historical evidence (Reeve 1994, 125) suggests that pre-Hispanic societies in the Marañón-Huallaga area shared a salt-stone-based trading system, henceforth SBT. This is remarkable, since other adjacent language families, such as Quechua and Chicham, do not show such a pattern for the formation of their own numerals. We claim, tentatively, that these common trade networks may be the sociohistorical motivation for the diffusion of this calquing pattern in the area.